The present invention relates to a trigger valve controlling device and, more particularly, to a trigger valve controlling device for a pneumatic nail gun, a valve sleeve of the trigger valve which can detect an opening or closing status of a top air outlet of a cylinder, and an air driving passageway for controlling high pressure air to drive a hitting bar to reset.
A pneumatic nail gun having a pneumatic power source is a type tool used to drive nails into wood or some other kind of material. Usually, a safe sliding rod is arranged on a periphery of a gun body. The safe sliding rod is used to control operation sequence of hitting nails. The gun body has a plurality of main air chambers, a cylinder, a piston slidably connected in the cylinder, a hitting bar mounted to a bottom of the piston and a trigger valve for driving the hitting bar to hit nails therein. The main air chambers are configured to receive a high pressure air and keep a pressure of the high pressure air constant. The piston separates the cylinder into a top cylinder chamber and a bottom cylinder chamber. The top cylinder chamber is intercommunicated with a top air outlet of the gun body, and the bottom cylinder chamber is intercommunicated with a bottom air outlet of the gun body.
In use, a user can push the safe sliding rod and press the trigger valve so as to shift an air driving passageway of the high pressure air in the gun body, which makes the high pressure air flow through the air driving passageway and enter into the top cylinder chamber, thereby driving the piston and a piston rod mounted to a bottom of the piston to move downward to hit nails. In the meantime, the air in the bottom cylinder chamber can be exhausted via the bottom air outlet. After that, the user can release the safe sliding rod and the trigger valve so as to shift the air driving passageway. The high pressure air in the top cylinder chamber is exhausted via the top air outlet, and the high pressure air enters into the bottom cylinder chamber, thereby driving the piston and the piston rod mounted to the bottom of the piston to move upward to reset.
Among conventional technology about driving a hitting rod to move upward to reset, such as U.S. Pat. No. 5,911,351, teaches that an air chamber having a constant volume (also known as a return air chamber) is arranged on a periphery of a cylinder. The air chamber gathers a limited high pressure air from a top cylinder chamber when a piston in the cylinder moves downward. In the meantime, when the piston moves downward, the air chamber also gathers a residual air from a bottom cylinder chamber. After a user releases a safe sliding rod, the high pressure air in the air chamber is guided to the bottom cylinder chamber, which forms a power source to drive the piston and a hitting bar to move upward to reset.
However, due to a limited volume of the air chamber, a pressure of the high pressure air in the air chamber is smaller than that of the high pressure air required to hit nails. As a result, when the piston and the hitting bar are moved upward to reset, a speed of the piston and the hitting bar is not desirable. When the piston drives the hitting bar to move downward, gathering the high pressure air from the top cylinder chamber, or gathering the air residual in the bottom cylinder chamber, will reduce a power in the cylinder for hitting nails. Therefore, an efficiency and a smoothness of hitting nails are reduced.
In order to overcome above described questions, among a more advanced technology, a valve control device is disposed between a main cylinder chamber and a bottom cylinder chamber in a gun body. The valve control device can control a right time of the high pressure air driving the piston to move upward to reset. Particularly, when releasing the trigger and the safe sliding rod, the valve control device can open an air passageway of the main cylinder chamber and the bottom cylinder chamber. The high pressure air continuously enters into the bottom cylinder chamber to drive the piston to reset. However, a structure of the valve control device is complicated with too many components, so that a larger receiving space in the gun body is required. This also makes air passageways in the gun body be complicated so that it is difficult to manufacture the gun body and a manufacturing cost is high.